1. Field
The present invention relates generally to wireless communications and more specifically to synchronization in a wireless communication system.
2. Background
Wireless communication systems are widely deployed to provide various types of communication content such as, for example, voice, data, video and the like. Typically, commercial wireless communication systems use multiple-access techniques to allow multiple users to share the available system resources such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal frequency division multiple access (OFDMA) systems, and the like.
In a wireless communication system, a base station (BS) communicates with a user equipment device (UE) over a downlink path from the BS to the UE and over an uplink path from the UE to the BS. When a UE initially powers up, before it can either receive information over the downlink or transmit information over the uplink, its first action is typically to synchronize with the system. The process of synchronizing typically includes, among other things, acquiring system time as well as estimating and correcting frequency offset errors in the UE. For this purpose, a group of base stations typically transmits a common synchronization channel (sync channel) having a known symbol value. Upon initial system entry, a UE searches for the sync channel as a precursor to notifying the base station as to its presence in the system.
Because a UE cannot begin to communicate information over the system until it has achieved synchronization, it is advantageous for the user equipment device to expeditiously obtain synchronization upon initial system entry.